1. Technical Field of the Invention
The present invention relates to the manufacture of tires. More precisely, it relates to the placing of cords in order to form a tire reinforcement; and still more particularly, it proposes means and methods of manufacturing such a reinforcement on a form close to or identical to the shape of the internal cavity of the tire, i.e. a substantially toroidal form, supporting the blank of a tire during its manufacture.
2. The Related Art
In this technical field, methods and apparatus are already known for incorporating the manufacture of tire reinforcements in the assembly of the tire itself. This means that rather than having recourse to semi-finished products, such as reinforcement plies, one or more reinforcements are realised in situ while the tire is being manufactured and starting from a single reel of cord. Among these methods and apparatus, the solution described in U.S. Pat. No. 5,453,140 is particularly adapted to forming carcass reinforcements on a rigid core, whose outer face corresponds substantially to the shape of the internal cavity of the finished tire. In U.S. Pat. No. 5,453,140, an arrangement is shown wherein the cord, intended to form a carcass reinforcement, is placed in contiguous arches over a rigid core by an actuating system comprising an eyelet fixed to a chain mounted on pulleys so as to surround the core, forming a kind of ‘C’. By virtue of this actuating system, the eyelet effects a reciprocating movement about the core so as to deposit progressively and contiguously an arch with each outward, and an arch with each return, movement. With the aid of suitable pressers, the ends of the arches are applied gradually over the rigid core, which is pre-coated with raw rubber.
In order that the arches be placed as radially as possible in the sides, while imparting to the rigid core a smooth rotary movement, it is proposed that the pulleys supporting the chain be staggered around the circumference relative to a radial reference plane. However, such staggering can only ensure radial deposition for a single combination of speeds of the core and the chain, i.e. for a single number of radial arches deposited over the entire periphery of the tire. As soon as one departs from this standard configuration, adjustment of the trajectory is imperfect. It is then necessary either to put up with this or to adjust the position of the pulleys.
From U.S. Pat. No. 6,328,836, a device is known that is also provided for carcass reinforcement on a rigid core whose outer surface corresponds substantially to the shape of the internal cavity of the finished tire. The actuating system comprises an arm oscillating around an axis of rotation substantially centered on the radial section of the torus formed by the core, the cord emerging at the end thereof in order to be deposited in contiguous arches on a rigid core. In order to control the deposition trajectory of the arches in the sides, U.S. Pat. No. 6,328,836 proposes to pass the cord between two cord-guides located opposite the sides. U.S. Pat. No. 6,328,836 also proposes to impart to the core a jerky rotary motion. Taking into account the inertia of the core, this is not without practical problems, which are all the more acute since it is desired to operate at rapid deposition rates.